Apparatus for mixing hot and cold liquids



Aug. 4, 1942. T. o. WILTON 2,292,256

APPARATUS FOR MIXINQ HOT AND COLD LIQUIDS Filed Aug. 14, 1940 Patented Aug. 4, 1942 APPARATUS FOR MJXIN G HOT AND COLD LIQUIDS Thomas Owston- Wilton, Horsham, England Application August 14, 1940, Serial No. 352,592 In Great Britain March 11, 1940 Claims.

This invention relates to apparatus for mixing hot and cold liquids and it has for its object an improved construction of such an apparatus and, particularly, of the portion of the apparatus for carrying out processes for the distillation of tar, oils and like liquid hydrocarbons in which cold or pre-heated crude materials are mixed with hot residues for the purpose of vaporising the constituents of relatively low boiling points.

In the processes of tar distillation referred to above, difiiculties have been experienced owing to frothing of the mixed materials at and in the vicinity of the point where they are brought in contact. The cause of this frothing has been found to be due to the intensive formation of vapours in the mass of the crude incoming materials, due to the heat of the residues, at the point referred to, together with the restricted area over which the first contact of the crude materials and the hot residues takes place.

One of the features of my invention is to effect the mixture of the materials at a plurality of points distributed in superposed sections of the distilling column in which the mixing took place, in plants such as referred to, for example at three or more sections at the top of this column; another feature is to cause one of the materials to be mixed, or both of them, to spread over a relatively large areain each section before bringing them in contact, for example by causing one of them to flow on to theother over the edges of the area it covers. In this manner, the action of the hot residues on the relatively cold incoming crude materials is distributed over a relatively large area, so as to offer the latter materials a relatively large surface at which vapours are liberated, thereby eliminating as much as possible the conditions causing frothling and achieving accordingly a marked improvement in the working of the plant.

According to myinvention, therefore, I provide a column divided vertically into a number of sections by horizontal partitions or trays provided with a preferably central flanged aperture to allow vapours to rise to the top of the column, provision being made to introduce one of the liquids to be mixed, preferably the colder one, at the bottom of a plurality of sections at the top of the column, so that the liquid spreads over the horizontal portion of the partitions of trays, the second liquid being introducedat or near the top of the said sections, so'as to fall on to the surface of the first liquid, thereby providing a number of points where the mixing and the 'heat exchange-takes place and a'relatively large area materials may flow over the edge of the central flanged aperture on to the bottom of the section below, or may be discharged thereon by suitably disposed constant level overflow orifices. The central apertures of the sections may have the same diameter or their diameter may decrease in the lower sections; the flange of these apertures is conical, so that when mixed materials overflow, it clings to the inner surface of the cone and drops on to the bottom of the section below, clear of its central aperture, or on to the inner surface of its flange and thence down this flange on the bottom of the section.

Each constituent is preferably admitted in each section by a plurality of inlets suitably distributed peripherally of the section, for example by two inlets diametrally disposed, the diameter at which the inlets of one constituent are disposed being at right angles to the diameter on which the inlet of the other constituent aresituated.

Instead of an annular circular ledge on to which one of the constituents is introduced to overflow on to the other constituent at the bottom of the section, it may be poured into an annular peripheral trough provided on the bottom of the section by a vertical or sloping ridge or wall on the partition or tray constituting the bottom of the section.

1' preferably cause the hot residues to flow on to the colder incoming materials inorder to avoid too much eifervescence, for the same reason as, when diluting sulphuric acid, one drops the acid into the water, and not the water into the acid, which would produce too intense a reaction. Alternatively, however, one may cause th incoming crude materials to overflow on to the hot residues spread on the bottom of the section.

A further advantage of the invention is that it enables the throughput of the plant to be increased without proportionally increasing the size of the mixingcolumn. Experience hasshown that it is not advisable to increase the height of this column above approximately 25 feet. In a mixing column of this height, by causing the mixed materials to flow over inclined trays or baiiies so that it follows a zig-zag path, it has been found possible to give to this path a length of approximately 40 feet, which seems to be the limit which it is not convenient to exceed. Once this limit is reached, if it be sought to increase the throughput of the plant by increasing the rate of flow of the hot residues and of the crude materials, in the case of the distillation processes referred to above, frothing troubles cannot be avoided, as has been mentioned.

By using a mixing tower constructed according to the invention, however, the throughput can be increased relatively considerably without this drawback being met with.

Referring to the accompanying drawing, which shows, as examples only, several manners of construction of a mixing column according to the invention, adapted for use in connection with a tar distilling plant in which crude materials, preferably pre-heated, are subjected to a preliminary distillation by being mixed with hot residues having already passed through the distilling zone of the plant:

Fig. 1 is a sectional elevation of a mixing column according to the invention;

Fig. 2 is a transverse section of the mixing column;

Fig. 3 is a sectional elevation of an alternative construction of the top of the mixing column;

Fig. 4 is a sectional elevation of an alternative form of section of the mixing column;

Fig. 5 is a part sectional elevation of yet another form of section;

Fig. 6 is a part sectional elevation of a modification of the section shown in Fig. 5, the section being by a plane at right angles to the plane of the section shown in Fig. 5.

In the figures, l is a Vapor box at the top of the mixing column 2, and 3, 4, 5, 6, 1 are successive sections down the column; 3' (Fig. 3) is an alternative form of section to be used with the arrangement of vapour box shown in Fig. 3; 8 and 8 (Figs. 4 and 5 or 6) are alternative forms of sections which may be used instead of any one of the sections shown in Fig. 1. Materials heated in a still enter the vapour box by the inlet pipe 9, the vapours liberated in the vapour box escape by the outlet l0, while the hot residues flow down by the outlet pipes I l into the down-take pipes 12, whence they enter the sections of the mixing column by branch pipes l3, l4, 15, I6, l1 The crude material enters the mixing column by the inlet pipe l8, which branches into two down-take pipes l9, from which the material is led to the bottom of each section by branch pipes 20, 2!, 22, 23 The partitions 24, 25, 26, 21 between the sections are provided with a central aperture with conical flanges 24, 25', 26', 21 as shown. 28, 29, 30, 3| are constant-level overflow passages for the mixed materials filling the bottom portions of the sections and 32 is an outlet for vapours of relatively low boiling points liberated in the mixing column by the heat of the residues mixing with the crude material, which vapours rise in the mixing column from section to section up to the upper section, which is preferably deeper than the other sections below it.

In Fig. 3, 35 are overflow passages for hot residues from the vapour box I, there being downtake pipes for the crude material only, as shown in Fig. 1, the mixed crude material and residues flowing down from section to section by the overflow passages 28, 29, 30, 3| The diameter of the passages 28, 29, 30, 3| are of suflicient diameter to allow the flow of the mixed ma-' terials after entering the sections by the inlet branches from the down-take pipes in the arrangement of Fig. l, or from the two passages 35 and the inlet branches from the down-take pipes 19, in the arrangement of Fig. 3, as well as the mixed materials which overflow from the section or sections whose position is higher; they consequently increase in cross section from section to section down the column; any material mixed in any section, which does not find a passage downwards through these passages, flows over the edge of the conical flanges 24, 25', 26', 21 which edge may be serrated or milled to facilitate this flowing over; the materials flowing over in this fashion cling to the inner surface of the cones and drop on to the outer surface of the cones of the flanges of the sections which are immediately underneath.

InFig. 4, 35 is a flanged annular peripheral ledge adapted to receive the hot residues, which then flow over the edge of the flange of this ledge, which may be serrated or milled, and drop on to the crude material spread on the bottom of the section, underneath the said ledge.

In the arrangements shown in Figs. 5 and 6, 36 is an annular peripheral trough formed by a wall or ridge 36 on the bottom of the section. The hot residues enter by the inlet branch pipes [3, while the crude materials are led, by extensions 20' to the inlet branch pipes 20, into the trough formed by the remaining portion of the section, between the said wall and ridge and the central flanged aperture. In Fig. 5, the wall or ridge is inclined and in Fig. 6 it is vertical; the former arrangement is preferable as, with it, the residues flowing over the serrated or milled edge 36 of the wall or ridge 36 fall free of the foot of the said wall or ridge, on to a larger area of crude material spread on the bottom of the inner trough. It will be seen that the crude material in this inner trough is also heated by the heat of the hot residues in the outer trough, which heat passes by conduction through the metal of the wall or ridge. The mixed materials in the inner trough flow into the next section down by the passages 28.

Two down-pipes have been shown for the hot residues and two down-pipes for the incoming crude material; there may be more than two, or there may be only one; particularly, one is sufficient in the arrangements shown in Figs. 4, 5 and 6, where an extensive area of contact by overflow is provided. There may also be a separate down-take pipe for the residues from the vapour box to each section of the mixing column where incoming crude material is mixed with hot residues.

The apparatus described above is particularly suited for a number of industrial processes, and, among these, may be specially mentioned the tar distillation processes referred to in the specification. It may advantageously be used, with slight modifications, for mixing any kinds of liquids; if the liquids do not liberate vaporisable constituents, the vapour box and the opening 32 are omitted.

What I claim is:

1. An apparatus for mixing hot and cold liquids, comprising a mixing tower constituted by a plurality of horizontal sections separated by annular trays the central opening 'of which is provided with a flange, inlet pipes for the incoming cold material, opening near the bottom of each section, inlet pipes for the incoming hot material, opening near the top of each section and overflow passages for the mixed materials from each section to the section next lower down.

2. An apparatus for mixing hot and cold liquids, comprising a mixing tower constituted by a plurality of horizontal sections separated by annular mixing trays the central opening or which is provided with a flange, one down-take pipe for the incoming crude material and one down-take pipe' for the incoming hot material, said down-take pipes being disposed along the said mixing tower, branch pipes from said downtake pipes to the sections of said tower and overflow passages for the mixed materials from each section to the section underneath it.

3. An apparatus for mixing hot and cold liquids, comprising a mixing tower constituted by a plurality of horizontal sections separated by centrally apertured trays, a flange to the inner edge of said trays, an annular wall on the bottom of said trays, forming two annular troughs thereon, inlet pipes for the incoming crude material, extending over the outer trough and opening over the inner trough, inlet pipes for the incoming hot material, opening in the outer trough, and overflow passages from each inner trough of a section into the inner trough of the section immediately underneath.

4. An apparatus for mixing hot and cold liquids, comprising a mixing tower constituted by a plurality of horizontal sections separated by flanged annular trays, an annular wall on each said tray, dividing it into two annular troughs, said wall sloping towards the centre of the tray, inlet pipes for the crude material and for the hot residues, opening over the inner trough and on to the outer trough, respectively, and overflow passages from each inner trough to the inner trough of the section immediately below it.

5. An apparatus for mixing hot and cold liquids, comprising a mixing tower constituted by a pluralit of horizontal sections separated by annular trays provided with a flange on their inner edge, an annular wall on each said tray, approximately equidistant'from the periphery of the tray and the flange thereon, said wall having a serrated edge, and pipe inlets for cold liquid opening over the inner portion of the tray and for hot liquids opening into the outer portion of the tray and overflow passages from any tray to the tray below it.

6. An apparatus for mixing hot and cold liquids, comprising a mixing tower constituted by a plurality of horizontal sections, an annular plate constituting the bottom of each section, a flange on the inner edge of said annular plate, a circular ridge on said plate, higher than the said flange and inlet pipes for the cold and the hot liquids to be mixed, opening on either side of said ridge above the said plate.

7. An apparatus for mixing hot and cold liquids, comprising a plurality of horizontal circular sections superposed to form a column, internally flanged annular plates between each section, a peripheral flanged ledge internally of the cylindrical wall of each section, overflow passages through the plate forming the bottom of each section, well within the circle formed by the flange of the ledge and inlet pipes for the hot liquid opening on to the said ledge and for the cold liquid opening on to the section below the ledge.

8. An apparatus for mixing hot and cold liquids, comprising a plurality of superposed horizontal circular sections separated by annular plates flanged on their inner edge, a, peripheral ledge on the inner cylindrical wall of each section, a flange with a serrated edge on each said ledge, overflow passages through said plates and inlet pipes for the hot liquid opening on to said ledge and for the cold liquid opening on to the annular plate below said ledge.

9. In an apparatus for the distillation of tar, a mixing tower for the incoming crude tar and hot pitch residues, constituted by superposed horizontal sections, a centrally apertured and flanged bottom to each section, a vapour box at the top of the column, passages in the floor of the vapour box for the pitch residues from the said vapour box to the section immediately below it, overflow passages through the floor of each section to the section immediately under it and inlet pipes for the incoming crude material opening into each section.

10. An apparatus for mixing hot and cold liquids comprising a mixing tower constituted by a plurality of superposed horizontal sections separated by annular trays provided with a conical flange on their inner edge, inlet pipes for the incoming cold material, opening near the bottom of each section, inlet pipes for the incoming hot material, opening near the top of each section and overflow passages for the mixed materials from each section to the section next lower down.

THOMAS OWSTON WilILTON. 

